The ability to understand disease in terms of the disruption of function in healthy cells is frequently limited by our knowledge of the functional architecture of normal tissue. This knowledge is gained slowly because tools for studying cell structure have been either very tedious to use (electron microscopy) or ineffective in cells of normal thickness (conventional light microscopy). The aim of this proposal is to acquire a system for studying the 3D functional architecture of cells based on the revolutionary new techniques of confocal light microscopy. This system will be utilized by a core user group of seven cell biologists and neurobiologists who collectively are engaged in five major areas of research. These are 1) role of c-oncogenes in cell growth and differentiation; 2) early steps in the development of heart and skeletal muscle; 3) neural organization subserving the processing of visual information in the retina; 4) structural features of the myosin molecule responsible for the assembly of thick filaments of skeletal myofibrils and 5) pathways and molecules involved in the formation of contractile structures in muscle and non-muscle cells. The subjects studied by this core user group are diverse. However, we share the need for a rapid way of studying cell architecture in the 0.1 to 1.0 mu resolution range, a way that is not rendered useless by tissue thickness in the range 0.1-0.5 mm. We have jointly explored the use of laser scanning confocal microscopy and found that this newly developed technique opens up exciting new possibilities for our research.